Peering into the Heart of Darkness with VLBA: Radio-quiet Active Galactic Nucleus in the JWST North Ecliptic Pole Time-domain Field
Bibliographic record
Abstract
Abstract We present initial results from the 4.8 GHz Very Long Baseline Array (VLBA) survey of the JWST North Ecliptic Pole Time-Domain Field (TDF). From 106 radio sources found in the Karl G. Jansky Very Large Array (VLA) observations in the TDF, we detected 12 sources (∼11% detection rate) at ∼3.3 μJy rms sensitivity and ∼4 mas resolution. Most detections exhibit parsec-scale emission (less than 40 pc) with high VLBA/VLA flux density ratios and brightness temperatures exceeding 105 K, confirming nonthermal active galactic nucleus (AGN) activity. Spectral indices α ≳ −0.5 correlate with higher VLBA/VLA flux ratios, consistent with synchrotron emission from AGN coronae or jets. In the majority of our sources, star formation contributes less than 50% of the total VLBA radio emission, with a few cases where the emission is almost entirely AGN driven. Although the radio emission from radio quiet AGN is thought to be primarily driven by star formation, our VLBA observations confirm that there is also often a contribution at various levels from black hole driven AGN. Eight VLBA detections have JWST/NIRCam counterparts, predominantly early-type, bulge-dominated galaxies, which we use to get an estimate of the redshift and star formation rate (SFR). Wide-field Infrared Survey Explorer colors indicate that VLBA detections are either AGN or intermediate-disk-dominated systems, while VLBA nondetections correspond to extended, star-forming galaxies. We compare SFRs derived from previous SCUBA-2 850 μm observations with new JWST-based estimates, and discuss the observed discrepancies, highlighting JWST’s improved capability to disentangle AGN activity from star formation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.007 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".